Techniques for the preparation of highly fluorinated polyethers

ABSTRACT

A process for preparing a fluorinated poly(arylene ether) comprising the repeating unit:  
                 
 
     wherein n provides a molecular weight up to about 30,000 to 100,000, X represents one of following groups: none, ketone, sulfone, sulfide, ether, hexafluoroisopropylidene, αω-perfluoroalkylene, oxadiazole, and Y is 4,4′-(hexafluoroisopropylidene)-diphenyl, 4,4′-isopropylidene diphenyl, 3,3′-isopropylidene diphenyl, phenyl, or chlorinated phenol which process comprises reacting a bis(pentafluorophenyl) compound and a bisphenol or hydroquinone in the presence of a dehydrating agent and a polar aprotic solvent is disclosed. Polymers resulting from the process show good promise as new passive optic polymer waveguide materials.

[0001] This application is a National Stage application of PCTApplication PCT/CA03/00779 filed May 28, 2003 which claims benefit ofU.S. Provisional Application 60/383,148 filed May 28, 2002 and U.S.Provisional Application 60/433,574 filed Dec. 16, 2002.

BACKGROUND OF THE INVENTION

[0002] There is a growing interesting in the development of new passiveoptic polymer waveguide materials for telecommunication applicationssuch as a thermo-optic switching, optical wavelength filters, beamsplitters, optical connectors and arrayed waveguide gratings (AWG).Polymers, because of their excellent low-temperature processability andtheir ability to be chemically modified or blended with other polymers,are ideal candidates as waveguide materials, since the opticalproperties can be tailored to requirements. Polymer waveguides alsooffer the potential to be incorporated into highly complex integrateddevices and optical interconnects on a planar substrate.

[0003] The requirements for the ideal passive optical polymer materialare:

[0004] Low optic loss at 1.3˜1.55 μm.

[0005] Low birefringence, Δn<5×10⁻⁵.

[0006] Adjustable refractive index.

[0007] Crosslinkable (photo- or thermal-).Good substrate adhesion.

[0008] High mechanical strength.

[0009] High Tg (>120° C.).

[0010] Good processing properties (coating, etching, dicing, etc.)

[0011] High durability when incorporated into a device (e.g. high Tg,low water up-take, high chemical and environmental resistance.

[0012] Many attempts have been made to produce polymers that meet theabove criteria. For example, several polymers have been prepared inwhich fluorine or deuterium has been used to replace hydrogen in themolecular structure. Polymers prepared with these substituents have beenshown to reduce optic losses. However, when these materials have beentested in optic waveguides applications, only a few have shownsatisfactory performance (these materials are summarized in Table 1). Interms of waveguide applications, the polymers based upon the fluorinatedpolyethers (FPAE and FPEK) are considered to be the best candidates,since they offer materials with: low optic loss, low birefringence, andgood mechanical properties. However, based upon the “ideal” criterialisted above, it should be noted that even these materials fail to meetthe criteria for optic loss and birefringence. TABLE 1 Polymers used forplanar passive optic waveguides loss, Tg 1.55 mm Polymer (° C.) (dB/cm)N Δn notes PFPs-PGMA 82-97 0.42  1.46-1.475 4 × 10⁻⁴ RIT, SwedenF-polyacrylate 100-150 0.6 1.3˜1.5 AlliedSignal PFCB 120-350 0.21.46-1.54 Clemson U. Dow FPAE 167(240)* 0.2 1.495-1.530   7.8 × 10⁻³Korea FPEK 149(202)* <0.5   1.51   1.4-4.6 × 10⁻³ Monash U. Koreapolycyanurate ˜250 0.6 ˜1.51 Germany Cl-Polyimide 0.4 1.51-1.57   1.0 ×010⁻² Korea F-Polyimide 0.5 1.52-1.55   0.57-1.58 × 10⁻² Korea

[0013] In terms of chemical structure, one way to achieve a low opticalloss material is to replace the hydrogen atoms in a polymer structurewith fluorine atoms. Consequently the fluorinated polyethers (FPAE andFPEK), listed in Table 1, would be expected to have the lowest opticallosses because they have higher fluorine content. Meanwhile, in order toobtain materials with variable refractive index the chemical structureof the polymers can be modified. This can be achieved by theincorporation of aliphatic groups, which will reduce the refractiveindex, or alternatively using aromatic groups, which increase thepolymers higher refractive index. In addition a factor that affects apolymeric materials the birefringence is the chain orientation. Reducingthe orientation in a polymer yields materials with low birefringence.The following represent ways of reducing the orientation to achieve alow birefringence material:

[0014] Highly flexible polymer chain.

[0015] Lower glass transition temperature polymers. However, it shouldbe noted that this conflicts with the reliability of the device. Thelowest Tg recommended for a durable reliable device is 120° C.

[0016] Low processing temperature (crosslinking, annealing, etc.)

[0017] Kim et al in Macromolecules (2001), 34:7817-7821 describe aprocess for preparing fluorinated poly(arylene ether sulfide) forpolymeric optical waveguide devices employing a high temperature (120°C.) to ensure complete dehydration.

[0018] U.S. Pat. No. 6,136,929 (Han et al) discloses a method for makingpolyarylene ethers employing K₂CO₃ at 80° C. for 24 hours.

[0019] Japanese patent, JP2002194082 (Lee et al) discloses thepreparation of fluorinated poly(arylene ether sulfide) and poly(aryleneether sulfone) for polymeric optical waveguide devices using azeotropicdistillation at 120° C. for the removal of H₂O.

[0020] One of the drawbacks of the published techniques for theproduction of fluorinated polyethers is the high tendency of the sidereaction on the ortho-position of bis(pentafluoro phenyl) compounds,which leads to branching structures and even crosslinked microgels inthe products.

[0021] There are 10 fluorines in the bis(pentafluorophenyl) compounds,and both para-and ortho-fluorines are reactive in the polycondensationreaction. Any reaction of ortho-fluorines will cause undesirablebranching and even crosslinking structures, which is detrimental for theoptical applications. Therefore, for preparing useful linear polymers,the selectivity of the reaction to the para-fluorines should be high.

[0022] Unfortunately, for the monomers with electron withdrawing groupsuch as ketone, sulfone or oxadiazole as the X group (see Scheme 1), theselectivity is relative poor, and large amount branching structures,even crosslinked microgels were proved to form in the products by usingthe above mentioned techniques if the polymers with high molecularweight were prepared.

[0023] In the present invention, the polycondensation reaction wasinitially modified by the addition of a dehydrating thimble filled withmolecular sieves or calcium hydride to dehydrate the condensed solventfrom refluxing, which enables the preparation of linear polymers from awide range of monomers with different linkage group X as listed inScheme 1.

[0024] The polycondensation reaction has been further modified by usinga CaH₂ mediated technique. This modified reaction is especially good forthe preparation of the fluorinated aromatic polyethers from activatedbis(pentafluorophenyl) compounds with electron withdrawing group (suchas ketone, sulfone or oxadiazole) as the linkage unit X.

[0025] We have found that this novel process offers a wide range ofadvantages over existing processes. These include the following: mildreaction condition, less side reaction, the obtained product is free ofany gel particles, white in colour, and the reaction is simple, fast andhas a high degree of reproducibility and is easy to control and thereaction is applicable to many starting materials as described in Scheme1 (see below).

[0026] Another drawback of the published techniques relates to the meansof achieving the crosslinkability of the polymers. Because crosslinkablepolymers have to be used in waveguide fabrication, crosslinking groupshave to be introduced into polymers at the chain end or as side pendantgroups. Based upon published information, only phenyl ethynyl or ethynylgroups have been suggested as the means of introducing crosslinkingability to the polymers. The reactions associated with these techniquesinvolve a two-step process. First the polymer has to be prepared andpurified, and then the purified polymer can be reacted with 4-phenylethynyl phenol (PEP) or with 3-ethynylphenol (EP) to yield thecrosslinkable polymer with the crosslinker at the chain end.

[0027] There are several disadvantages associated with this technique:

[0028] Of the polymers prepared using this approach (only two) one isbelieved to have high impurity content making its use impractical fornormal applications.

[0029] The crosslinking group is only attached to the chain end, thusits content in polymer is limited to a very low level.

[0030] PEP and EP are not commercial available and are difficult toprepare.

[0031] PEP and EP are not fluorinated compounds and the resultantpolymers possess low fluorine content which give higher optical lossmaterials.

[0032] The polymers have to be cured at high temperatures (350° C. forPEP polymer and 250° C. for EP polymer), which results in the formationof cured materials with high birefringence. In addition the curing athigh temperature causes increases the chances of side reactions such asoxidation. These side reactions contribute to larger optical losses.

[0033] The process of this invention provided a simple approach forintroducing crosslinkable fluorostyrene moieties as shown in Scheme 1into the polymers with an adjustable concentration by a one-potreaction. Comparing to the published techniques, this inventionpossesses following advantages for the process and materials:

[0034] (a) The product is obtained as a pure white polymer with a lowPDI.

[0035] (b) The product is free of any crosslinked structures

[0036] (c) Polymers with higher molecular weight are possible (Mw˜50,000Da)

[0037] (d) The process is suitable for introducing FSt into polymer forcrosslinking.

[0038] (e) The contents of FSt in the polymer are variable and can be asdesigned.

[0039] (f) The product is photo- and thermally-crosslinkable.

[0040] (g) Low or high curing temperatures could be employed (ambienttemperature to 250° C.).

[0041] (h) The product has an idealized Tg (e.g., 140° C. before curing,170° C. after curing for FPEK-FSt, and 163° C. before curing, 191° C.after curing for FPESO-FSt)

[0042] (i) The product has a low birefringence.

[0043] (j) A range of polymers can be prepared covering a wide range ofrefractive index.

[0044] (k) The product produces uniform films, with excellentreproducibility in their optical properties (see below).

[0045] Most of the published synthetic techniques involve using K₂CO₃ orother alkali carbonate to neutralize HF that is produced in thereaction, and thus H₂O is produced from the reaction. It has to beremoved from the solution in order to complete the reaction and toeliminate the side reactions such as hydrolysis caused by H₂O.Azeotropic distillation are a common used technique for this purpose inthe preparation of fluorinated poly(arylene ethers). However, thistechnique can not sufficiently remove H₂O from the reaction and thussevere reaction conditions (high temperature, long reaction time) haveto be employed in order to yield a high conversion for high molecularweight polymers. This severe condition causes side reactions(hydrolysis, cleavage, cyclization, oxidation, etc.), and lead topolymers with lower MW, high PDI and colour. On the other hand, for theazeotropic distillation, non-polar solvent, benzene or toluene has to beintroduce into the reaction, which will reduce the selectivity of thereaction on the para-position of bis(pentafluorophenyl) compounds, andresults in higher content of branching and even crosslinking structures.

SUMMARY OF THE INVENTION

[0046] According to the invention there is provided a process forpreparing a fluorinated poly(arylene ether) comprising the repeatingunit:

[0047] wherein n provides a molecular weight up to about 30,000 to100,000, X represents one of following groups: none, ketone, sulfone,sulfide, ether, hexafluoroisopropylidene, αω-perfluoroalkylene,oxadiazole, and Y is 4,4′-(hexafluoroisopropylidene)-diphenyl,4,4′-isopropylidene diphenyl, 3,3′-isopropylidene diphenyl, phenyl, orchlorinated phenol which process comprises reacting abis(pentafluorophenyl) compound and a bisphenol or hydroquinone in thepresence of a dehydrating agent and a polar aprotic solvent. By way ofexample the dehydrating agent may be selected from the group consistingof a molecular sieve, NaH, CaH₂, CaO, silica gel, activated Al₂O₃,CaSO₄, MgSO₄, and Na₂SO₄. In preferred embodiments the polar aproticsolvent is selected from the group consisting of dimethyl acetamide,dimethyl sulfoxide, N-methyl-2-pyrrolidone (NMP), dimethyl formamide andpropylene carbonate.

[0048] The process of the invention may be carried out in the presenceof an alkali metal salt such as a fluoride. Preferably the alkali metalsalt is selected from the group consisting of KF, RbF, and CsF.

[0049] Alternatively the alkali metal salt may be a carbonate. Forexample the alkali metal carbonate may be selected from the groupconsisting of Na₂CO₃, K₂CO₃, Rb₂CO₃ and Cs₂CO₃.

[0050] The process of the invention may be mediated by CaH₂ or CaO andin the presence of such a catalytic amount of an alkali metal salt suchas one of the fluoride salts referred to above in such a polar aproticsolvent.

[0051] Under certain circumstances it may be useful to carry out theprocess of the invention in the presence of areflux-temperature-reducing co-solvent. Preferably the co-solvent isselected from the group consisting of toluene, benzene andtetrahydrofuran.

[0052] The process of the invention may be carried out in such a mannerthat the dehydrating agent is contained in a thimble between a reactionflask and a condenser so that condensed solvent from refluxing passesthrough the dehydrating reagent. The invention also relates to a processfor preparing a tetrafluorostyrene comprising a polymer or oligomer ofthe formula:

[0053] in which n provides a molecular weight up to about 30,000 to100,000, X represents one of following groups: none, ketone, sulfone,sulfide, ether, hexafluoroisopropylidene, αω-perfluoroalkylene,oxadiazole, and Y is 4,4′-(hexafluoroisopropylidene)-diphenyl,4,4′-isopropylidene diphenyl, 3,3′-isopropylidene diphenyl or—CH₂(CF₂)₂₋₁₂CH₂— which process comprises reacting pentafluorostyrenewith bisphenol and then with a bis(pentafluorophenyl) compound in thepresence of a dehydrating agent and a polar aprotic solvent. Such aprocess can be carried out as a one-pot reaction.

[0054] The invention additionally relates to a process for preparing afluoropolymer comprising fluorostyrene residues as end-caps or aspendant groups of the formula

[0055] wherein n, X and Y are as defined above and m is from 1 to 20which process comprises polymerizing a compound of the formula 1 or 2

[0056] with a bis(pentafluorophenyl) compound as a one-pot reaction inthe presence of a dehydrating agent and a polar aprotic solvent.Compounds 1 and 2 may be present in a predefined ratio.

[0057] The invention also concerns a crosslinkable highly fluorinatedoligomer, a poly(arylene ether) or a poly(alkylene arylene ether) withfluorostyrene residues as end-cap groups or pendant groups in theoligomer or polymer, said oligomer or polymer having the formula:

[0058] a. Oligomers

[0059] b. Crosslinkable Polymers with FSt Groups End-Capped

[0060] c. Crosslinkable Polymers with FSt End-Capped and Pendant Groups

[0061] wherein n and m are as defined above and

[0062] Additionally the invention concerns a highly fluorinatedpoly(arylene ether oxidazole) comprising repeating units of the formula:

[0063] wherein n and Y are as defined above.

[0064] In Method 1 we disclose the use of molecular sieves or CaH₂ asdehydrating agents for the sufficient removal of H₂O from the reaction.This technique greatly promoted the reaction and allowed the reaction beconducted at milder reaction conditions and as a result it enhanced theselectivity of the reaction for the formation of linear polymerstructure. This technique make it possible to prepare linear polymersfrom highly activated monomers such as thebispentafluorophenyl-compounds with the linkage group X as sulfone andoxadiazole.

[0065] However, in this technique, the reaction has to be conducted withrefluxing in order to delivering water into vapour phase so that thewater can be removed by the absorption of molecular sieves or calciumhydride. In this case, a low boiling point solvent such astetrahydrofuran can be used to bring the refluxing temperature down forgood control of the reaction. However, this kind of solvent is usuallyof lower polarity then commonly used solvents such as DMAc forpolycondensation. This results in a poor selectivity of the reaction andless reactivity of monomers and thus reduces the reaction performance,i.e. producing polymers with a certain amount of branching structures.Such branching structures are detrimental for optical applications.Further improvements to overcome these shortcomings have been made.

[0066] The improvement in Method 2 is based on introducing CaH₂ or CaOinto the reaction solution itself so that the by-product of thereaction, HF could be immediately and efficiently removed withoutproducing H₂O. This modification significantly pushes the reactionequilibrium to the product side. Thereby the reaction is effected inextremely mild reaction conditions, which efficiently prevented the sidereactions including branching, crosslinking, hydrolysis, and oxidation.Additionally, CaH₂ or CaO acts as a mediator to the reaction by forminga CaF₂ precipitate thereby reducing the concentration of fluorine ion inthe solution. Fluoride ion was proved to catalyse side reactions such aschain cleavage. Therefore this method by use of CaH₂ combined with acatalytic amount of K⁺, Rb⁺, or Cs⁺ in the solution offers a muchsimpler and more efficient way for the preparation of fluorinatedpolymers. Due to the better selectivity of the reaction to thepara-fluorines in the bis(pentafluorophenyl)-compounds, polymers withlinear structure, higher molecular weight (up to 100,000 Da ) and freeof any crosslinked microgels have been obtained.

[0067] This invention also proved that a solvent with higher polaritysuch as propylene carbonate (PC, comparing to DMAc)) give betterselectivity for preparing fluorinated polymers, and thereby offerpolymers with higher MW and lower PDI.

[0068] A very important contribution of this invention is that thisprocess can easily introduce crosslinking groups, such as fluorostyrenemoieties, into the polymers with an adjustable concentration in themanner as shown in Scheme 1 to offer the polymer a crosslinkingcapability. The obtained polymers can be thermally- or photo-cured atdifferent temperatures (25-250° C.) with or without initiators to formhigh quality waveguide structures.

[0069] Therefore, a series of fluorinated polyethers and polyetheroligomers has been prepared. Most of them are easily dissolved in mostcommon solvent such as THF, cyclohexanone, DMF etc. Also, they aremiscible each other. These materials can span a wide range of refractiveindices. High quality uniform films for waveguide application have beenprepared by spin-coating the solution of the crosslinkable polymer orthe mixture of the polymers and/or oligomers followed by thermal or UVcrosslinking. The refractive index of the polymer film is adjustable ina range of 1.46 to 1.54 by varying the relative amount of polymers andoligomers with different refractive index in the mixture.

BRIEF DESCRIPTION OF THE DRAWINGS

[0070]FIG. 1 shows GPC curves of fluorinated polyether sulfone atdifferent times from the reaction techniques of: (A) molecular sievedehydration in vapour phase, reacted at reflux (84° C.); (B) CaH₂mediated, reacted in DMAc at 70° C.; (C) CaH₂ mediated, reacted in PC at60° C.

[0071]FIG. 2 shows GPC curves of fluorinated polyether ketone atdifferent times from the CaH₂ mediated reaction. Reaction condition:Bis(pentafluorophenyl) ketone (BPK)/6F-BPA (3.00/2.95, molar ratio), inDMAc at 70° C. with 20% KF (molar ratio to bisphenol) for 0.5, 1.5, 2.5,4.0, 6.0 hr.

[0072]FIG. 3 shows GPC curves of fluorinated polyether oxadiazole atdifferent times from the CaH₂ mediated reaction. Reaction condition:Bis(pentafluorophenyl) oxadiazole (BPOx)/6F-BPA (3.00/2.95, molarratio), in PC at 64° C. with 20% KF (molar ratio to bisphenol) for 1, 3,3.5, 4, 5, 6 hr. the sample was either washed with H₂O, or MeOH asindicated.

[0073]FIG. 4 shows alkali metal ion effect on the reaction speed for thepreparation of fluorinated polyether sulfone (Cs⁺(▴), Rb⁺ (∘) and K⁺ (▪)FIG. 4a) and polyether ketone (K⁺ at 70° C.(∘) and Cs⁺ at 45° C.( ) FIG.4b) in DMAc.

[0074]FIG. 5 shows the increase of molecular weight of polymer with thereaction time at temperatures of 35 (♦), 45 (▴), 55 (∘) and 65 (▪) ° C.,when the reaction was conducted in DMAc in the present of 20% (molarratio to phenol) CsF.

[0075]FIGS. 6a and b show reaction time dependencies of molecular weightof fluorinated polyether sulfone prepared by CaH₂ mediated reaction inpropylene carbonate.

[0076]FIG. 7. Kinetics of the reaction between FSt and 6F-BPA;

[0077] This reaction produces three products at different levels: mono-,di-, and tri-substitution of FSt. The mono substitution is demanded forthe polymer with FST end-capped, a mixture of mono- and di-substitutionare required for the preparation of high FSt contented polymers with FStas both end-capped and pendant groups. However, tri-substituted productsare harmful as they cause branching and even crosslinking structure.

[0078]FIG. 7 shows 30˜40 min is a proper reaction time for the FStend-capped polymers for this step reaction. At this time the molar ratioof mono-/di/tri-substitutions is 93:6:0, while 200˜250 min is proper forthe polymers with FSt as both end-capped and pendant group.

[0079]FIG. 8. 19F NMR of FPESO prepared in PC at 70° C. in the presenceof CaH₂ and KF at the reaction time of (A) 2.0 hr, (B) 3 hr, (C) 5 hr,(D) 9 hr. (the signal in B, C, D, was enlarged 20 fold). FIG. 8 displays¹⁹F NMR spectra of FPESO. The peak at −63.8 ppm is attributed to CF₃group, and other two major peak at −137.4 and −152.1 ppm are attributedto the ortho- and meta-fluorines respectively in the polymer chains. Thearomatic region was enlarged, and the spectra at different reaction timewas compared. The results indicate the end-group related peaks at−137.0, −144.0 and −154.9 ppm do not have notable intensity change after6 hr reaction and mean no more chain propagation after this time. Atthis time the peak related to the possible side reactions (marked with*) is very weak. Even at extended reaction time (9 hr), the intensity ofthese peaks still less than that of end-group, indicating the structurerelated to the side reactions such as branching is less than 2 units perpolymer chain. This result obviously confirmed that the CaH₂ mediatedreaction sufficiently depressed the side reactions.

[0080]FIG. 9. Kinetics of the reaction for EPEK mediated by CaO andcatalyzed by KF in DMAc. (H₂O effect). H₂O is proved to cause sidereactions such as hydrolysis of ether linkages in this polymerization.This effect to the CaH₂ (or CaO) mediated reaction was verified by usingCaO as mediator, in which water was allowed to introduce the reaction.FIG. 9 showed the effect on the reaction kinetics of different CaO thatcontain different level of H₂O (w %, measured by TGA) as shown belowType of CaO Free H₂O H₂O as Ca(OH)₂ CO₂ as CaCO₃ Flame dried 0.00% 0.00%8.0% Vacuum dried 0.00%  2.0% 0.9% As-received 0.04%  3.7% 0.9%

[0081]FIG. 9 shows that the reaction speed increased with the increaseof the water content in the solution. Traces of water will efficientlypromote the reaction rate. However, with the water content level as highas 0.2% of the solution, a molecular weight reducing at the end ofpolymerization was found, indicating side reactions to cause chaincleavage. However, this side reaction seems depressed when the reactionwas conducted at lower temperature than shown in FIG. 9. in this case,high molecular weight polymers were obtained.

DETAILED DESCRIPTION OF THE INVENTION

[0082] Reaction Schemes:

[0083] 1. The Preparation of Linear Polymers.

[0084] Condition: Method 1, for FPESO, CaH₂ in Vapour, K₂CO₃ in DMAc/THF(1/2, v/v) at 80° C., 100 min.

[0085] Method 2, for FPESO, KF+CaH₂ in PC, 70° C., 6 hr.

[0086] 2. Fluorinated Poly(arylene Ether) with FSt End-Capper.

[0087] Condition:

[0088] Method 1. For FPEK, MS (in vapour)+K₂CO₃ in DMAc/Benzene(10/5,v/v) (i) 117° C., 40 min, (ii) 109° C., 20 min

[0089] Method 2. For FPEK, CaH₂+KF in DMAc (i) 120° C., 3 hr, (ii) 70°C., 3 hr.

[0090] For FPESO, CaH₂+KF in DMAc (i) 120° C., 3 hr, (ii) 70° C., 1.5hr.

[0091] 3. Fluorinated Poly(arylene Ether) with FSt as Chain Extender andEnd-Capper.

[0092] Method 1. For FPEK, MS (in vapour)+K₂CO₃ in DMAc/Benzene(10/5,v/v) (i) 117° C., 250 min, (ii) 106° C., 60 min

[0093] Method 2. For FPESO, (i) MS (in vapour)+K₂CO₃ in DMAc/Benzene(10/5, v/v), 117° C., 250 min,

[0094] (ii) CaH₂+KF in DMAc, 70° C., 1.5 hr.

[0095] In the present invention, basically two reaction methods havebeen presented. In Method 1, common reaction condition is modified byemploying dehydrating reagent in vapour phase to dry the condensedsolvents from refluxing, so that he reaction was promoted and theselectivity for the formation of linear structure was enhanced. InMethod 2, the polycondensation reaction have been modified by using aCaH₂ mediated technique, in which CaH₂ was added into the reactionsolution incorporated with a catalyst amount of alkali metal ion such asK⁺, Rb⁺ and Cs⁺. In this technique, CaH₂ acted as a base to neutralizethe HF produced from the reaction. It also acted as a precipitator toremove F by forming an insoluble CaF₂ precipitate. This modifiedreaction is especially useful for preparation of the highly fluorinatedaromatic polyethers with electron withdrawing groups (such as ketone,sulfone or oxadiazole) as the linkage group X. These effects are clearlyidentified by the experimental results demonstrated in FIG. 1. Thestarting materials and the resultant polymers and oligomers are listedin Scheme 1.

[0096] Scheme 1. The Structures of Starting Materials and ResultedPolymers and Oligomers.

[0097] a. Starting Materials

[0098] b. Linear Polymers

[0099] c. Crosslinkable Polymers with FSt Groups End-Capped

[0100] d. Crosslinkable Polymers with FSt End-Capped and Pendant Groups

[0101] e. Oligomers

[0102] Method 1. Polymerization by Dehydrating the Condensed Solvent.

[0103] A novel reaction device is provided by equipping a dehydratingthimble underneath the condenser in the reaction system, which wasfilled with anhydrous molecular sieves or CaH₂, so that the condensedsolvent will pass through the dehydrating reagent. Comparing to theprior art devices e.g. a Soxhlet extractor, the novel device provides asmooth reaction with well-controlled reaction temperature and solventcomposition during the reaction.

[0104] This device results in more efficient dehydration, so that thereaction can be done in milder conditions (lower temperature and shortreaction time). As a result, the possibility of side reactions(hydrolysis, cyclization, oxidation, etc.) is reduced. This method isappropriate for preparing many fluorinated, and non-fluorinated aromaticpolyethers.

[0105] Crosslinkable polymer containing fluorostyrene moieties have beenprepared by this process for fluorinated poly(arylene ethers) and by amethod using NaH for fluorinated poly(alkylene arylene ethers) asdemonstrated in Scheme 2. The relevant oligomers have also been preparedin a similar manner without using the decafluoro-compound.

[0106] The reaction for preparing FSt containing fluorinated polyethers(including polyarylene ether, polyether ketone, polyether sulfone, andpolyether sulfide) revealed that FSt is linked to the polymers in twodifferent ways simultaneously. One is as end-capped groups and the otheris as pendant groups. In the latter, FSt is actually inserted into thechain by forming two linkages at both the 2, and 4 positions of thebenzene ring in styrene. The reaction condition for introducing the FStat different level was described in FIG. 7. This enables us to preparefluorinated polyethers with crosslinkable vinyl groups as side pendantgroups as well as end-cappers. The loading density of FSt is adjustable.Due to the UV curability, these kinds of materials will be very usefulin the waveguide fabrication by using direct patterning with UVlithograph techniques.

[0107] Scheme 2. Polycondensation Reactions for the Preparation ofFluorinated Poly(arylene Ether)s and Fluorinated Poly(alkylene AryleneEther)s with FSt End-Capped.

[0108] a. Fluorinated Poly(arylene Ether)

[0109] b. Fluorinated Poly(alkylene Arylene Ether)

[0110] c. Fluorinated Poly(arylene Ethers) with High FSt Content

[0111] Condition: MS (in vapour)+K₂CO₃ in DMAc/Benzene (10/5,v/v) (i)reflux, 117° C., 150 min, (ii) reflux 106° C., 30 min.

[0112] The materials developed are useful as new passive optic polymerwaveguide materials for telecommunication applications such as athermo-optic switching, optical wavelength filters, beam splitters,optical connectors and arrayed waveguide gratings (AWG).

[0113] The different chemical structures of this series of fluorinatedpolyethers and polyether oligomers offer a wide range of materials withlow optical loss and a wide range of refractive indices. High qualityuniform films for waveguide application have been prepared byspin-coating the solution of the crosslinkable polymer or the mixture ofthe polymers and/or oligomers followed by thermal or UV crosslinking.The refractive index of the polymer film is adjustable in a range of1.46 to 1.54 by varying the relative amount of polymers and oligomerswith different refractive index in the mixture. The reproducibility ofthe optical properties of the crosslinked film from these materials isvery high.

[0114] As an example, the crosslinked films produced from the polymer,FPEK-FSt and its blends with HBPAE-FSt are very uniform and haveexcellent reproducibility in terms of their optical properties. Thisreproducibility can be seen in Table 2, which gives examples of a set ofmeasurements on refractive index and birefringence. The crosslinkedfilms of FPEK-FSt on different silicon wafers showed highlyreproducibility in terms of values for the refractive index andbirefringence. The average deviation for the measured RI values is only0.007%, which is at least 10 times better than the current appliedtechniques. Table 2. Refractive index and birefringence measurement ofpentafluorostyrene end-capped fluorinated poly(ether ketone) (FPEK-FSt)after curing. Sample # Thickness (μm) n_(TE)/n_(TM) Δ n 112.2800/12.3483 1.50194/1.49943 2.51 × 10⁻³ 2 10.3745/10.50271.50195/1.49933 2.62 × 10⁻³ 3 8.9083/9.0772 1.50195/1.49911 2.84 × 10⁻³4 7.2955/7.4976 1.50152/1.49901 2.51 × 10⁻³

[0115] Method 2 Calcium Mediated Polycondensation Reactions.

[0116] The presently known synthetic techniques involve using K₂CO₃ orother alkali metal carbonate to neutralize HF that is produced in thereaction, and thus H₂O is produced from the reaction. The followingmeans have been reported for removing H₂O and pushing the reactionforward:

[0117] High temperature with inert gas blowing

[0118] Azeotropic distillation

[0119] Inorganic dehydrating reagents in vapour or in solutionincluding, molecular sieves, silica gel, activated Al₂O₃, CaSO₄, MgSO₄,and Na₂SO₄.

[0120] Another known technique involves turning phenol to phenoxidealkali metal salt first, and then reacting with halide.

[0121] The various known processes suffer from the following limitationsor drawbacks.

[0122] Severe reaction conditions (strong causticity, high temperature,long reaction time) have to be used. They cause side reactions(hydrolysis, cleavage, cyclization, oxidation, etc.), and lead topolymers with lower MW, high PDI and colour.

[0123] The severe reaction conditions also cause branching andcrosslinking gel formation when activated decafluorodiphenyl-compoundsuch as decafluorobenzophenone, bis(pentafluorophenyl) sulfone was usedfor preparing fluorinated polymers.

[0124] In Method 1 we disclosed the use of molecular sieves or CaH₂ asdehydrating agents to remove water produced from the following reaction.This technique greatly promoted the reaction and allowed the reaction beconducted at milder reaction conditions and as a result it enhanced theselectivity of the reaction for the formation of linear polymerstructure and reduced the side reactions. This technique also make itpossible in first time to prepare linear polymers from highly activatedmonomers such as the bispentafluoro-compounds with the linkage group Xas sulfone and oxadiazole groups.

[0125] However, in this technique, a refluxing solvent system has to beused and the reaction has to be conducted at reflux temperature in orderto delivering water into vapour phase so that the water can be removedby absorption by molecular sieves or calcium hydride. In this case, alow boiling point solvent such as tetrahydrofuran preferably is used tobring the refluxing temperature down for good control of the reaction.However, this gentle solvent usually has a lower polarity then commonlyused solvents such as DMAc for polycondensation. This could result in apoor selectivity of the reaction and less reactivity of monomers andreduce the reaction performance, i.e. producing polymers with highercontent of branching structure. Such branching structures aredetrimental for optical applications. We have now developed furtherimprovements (Method 2) to overcome these shortcomings.

[0126] This improvement is based on introducing CaH₂ into the reactionsolution so that the by-product, HF can be immediately and efficientlyremoved. This modification significantly pushes the reaction equilibriumof polycondensation to the product side. Thereby the reaction iseffected in extremely mild reaction conditions, which efficientlyprevented the side reactions including crosslinking, hydrolysis,cyclization, and oxidation. Therefore, this method by use of CaH₂combined with a catalytic amount of K⁺, Rb⁺, or Cs⁺ in the solutionoffers a much simple and efficient way for the preparation offluorinated polymers. Due to the better selectivity of the reaction tothe para-fluorines in the decafluorodiphenyl-compounds, polymers withlinear structures free of any crosslinked gel particles have beenobtained.

[0127] CaH₂ in solution acts as a base to neutralize the acid, and as aprecipitating reagent to remove F⁻, both effects promoting the reaction,and reducing the tendency of side reaction. F⁻, if present in thesolution, acts as a strong catalyst for the side reaction such as thecleavage of the ether chain. The use of CaH₂ makes the reaction possibleat very mild reaction conditions, and also makes it possible to preparethe following fluorinated polymers with the molecular weight up to50,000 Da (Mn) with low MW distribution.

[0128] 1. Fluorinated poly(arylene ether sulfone),

[0129] 2. Fluorinated poly(arylene ether oxadiazole),

[0130] 3. Fluorinated poly(arylene ether ketone),

[0131] 4. Fluorinated poly(arylene ether sulfide),

[0132] 5. Fluorostyrene containing polymers (any of above polymers).

[0133] Also a new solvent (propylene carbonate) was found to give betterselectivity for preparing fluorinated polymers, and thereby offerspolymers with higher MW.

[0134] Reaction Schemes (for Some Optimised Reaction Conditions):

[0135] 1. The Preparation of linear Polymers.

[0136] Condition: (i) KF (or RbF, CsF)+CaH₂ in aprotic polar solvent(e.g. for FPESO KF+CaH₂ in PC, 70° C., 6 hr).

[0137] 2. Fluorinated Poly(arylene Ether) with FSt End-Capper.

[0138] Condition: CaH₂+KF in DMAc (i) 120° C., 3 hr, (ii) 70° C., 1.5hr.

[0139] 3. Fluorinated Poly(arylene Ether) with FSt as Chain Extender andEnd-Capper.

[0140] Condition: (i) CaH₂ (in vapour)+K₂CO₃ in DMAc/Benzene (10/5,v/v), 117° C., 250 min, (ii) CaH₂+KF in DMAc, 70° C., 1.5 hr.

[0141] In the present invention, the polycondensation reaction have beenmodified by using a CaH₂ mediated technique, in which CaH₂ was addedinto the reaction solution incorporated with a catalyst amount of alkalimetal ion such as K⁺, Rb⁺ and Cs⁺. In this technique, CaH₂ acted as abase to neutralize the HF produced from the reaction, and it also actedas a precipitator to remove F⁻ by forming an insoluble CaF₂ precipitate.F⁻ is proved to be detriment to the reaction by catalyze the sidereactions such as hydrolyzing and cleaving the chain. Therefore thismodified reaction is especially useful for preparation of the highlyfluorinated aromatic polyethers with electron withdrawing groups (suchas ketone, sulfone or oxadiazole) as the linkage group X. These effectsare clearly identified by the experimental results demonstrated in FIG.1

[0142] For FIG. 1, the reactions of bis(pentafluorophenyl)sulfone (BPSO)with hexafluorobisphenol A (6F-BPA) were conducted with the molar ratioof 3.00/2.95, so that the theoretical molecular weight of the designedpolymers is 41,600 Da. The molecular weight (Mn) of the final polymersfrom the reaction is around 21,000 Da, by considering some of cyclicoligomer contained in the polymers, these data are already very close tothe theoretical value. It should be noted that a broad shouldered peakwas found from the reaction with molecular sieves (FIG. 1A), thisshouldered peak related to the formation of branched structures, whilethis peak was reduced to a small tail from the CaH₂ mediated reaction inDMAc (FIG. 1B). It was further reduced and completely disappeared whenpropylene carbonate (PC) was used as the solvent (FIG. 1C).

[0143] A similar feature was also found when fluorinated polyetherketone and polyether oxadiazole were prepared by using the CaH₂ mediatedreaction in DMAc and PC respectively (see FIG. 2 and FIG. 3). For thepreparation of polymers containing highly activating group such asfluorinated polyether sulfone and polyether oxadiazole, from themolecular sieves dehydrating reaction, the formation of low content ofbranched structure is unavoidable if high molecular weight materials aredemanded. In contrast, CaH₂ mediated reactions significantly preventedthe formation of the branched structure in as shown in FIGS. 1 to FIG.3.

[0144] Kinetics of the Reaction.

[0145] 1. Concentration of Catalyst:

[0146] The effect of the concentration of KF as catalyst on the reactionspeed was tested. The results showed that the reaction speed increasedwith the concentration of KF in the reaction, and the rate leveled offwhen the amount of KF reached 10 mol % relative to the bisphenol.Therefore, 20 mol % of the KF was recommended for the reaction.

[0147] 2. Alkali Metal Ion, M⁺.

[0148] The reactivity of M⁺ to this reaction increased in the followingsequence Na⁺<K⁺<Rb⁺<Cs⁺. When NaF was used as catalyst, No polymer wasfound from the reaction. While, a significant reaction speed was foundwhen KF was used as catalyst in DMAc. FIG. 4 shows that reaction withCs⁺ is about 10 times faster that that with K⁺ for the preparation ofpolyether sulfone, and the reaction with Cs⁺ at 45° C. possess acomparable speed as the reaction with K⁺ at 70° C. for the preparationof polyether ketone.

[0149] 3. Counter Ion Effect:

[0150] The effect of the counter ion other than F⁻ such as Cl⁻ has beentested for this reaction. It is found that the presence of any amount ofCl⁻ will completely retard the reaction.

[0151] 4. Temperature Effect of the Reaction in DMAc by Using CsF asCatalyst.

[0152]FIG. 5 shows the reaction speed increased with the temperature ata rate of 6 folds per 10 degree. While the molecular weight andmolecular weight distribution did not show an obvious difference fordifferent temperature, indicating there is no significant side reactionat the tested temperature between 35 to 65° C.

[0153] 5. Solvent Effect,

[0154] Propylene carbonate (PC) has been tested for the reaction. Asindicated in FIG. 1, comparing to DMAc, reaction in PC produce polymerswith lower branch content, indicating a higher selectivity of thereaction. As shown in FIG. 6, MW increase with time in an exponentialmanner, indicating the solubility of K⁺ is very low in the solution.

[0155] It should be noted that light degradation was found at hightemperature (90° C.) when extended reaction time was used after thechain propagation finished.

[0156] 6. Branching Structures by Side Reactions

[0157] The formation of the branching structure was monitored by ¹⁹F NMRas shown in FIG. 8 for FPESO prepared in PC at 70° C. in the presence ofCaH₂ and KF at the reaction time of (A) 2.0 hr, (B) 3 hr, (C) 5 hr, (D)9 hr. (the signal in B, C, D, was enlarged 20 fold)

[0158] In these spectra the peak at −63.8 ppm is attributed to CF₃group, and other two major peaks at −137.4 and −152.1 ppm are attributedto the ortho- and meta-fluorines respectively in the polymer chains. Thearomatic region was expanded. The result indicates the end-group relatedpeaks at −137.0, −144.0 and −154.9 ppm do not have notable intensitychange after 6 hr reaction, means no more chain propagation after thistime. At this time the peak related to the possible side reactions(marked with *) is very week. Even at extended reaction time (9 hr), theintensity of these peaks still less than that of end-group, indicatingthe structure related to the side reactions such as branching is lessthan 2 units per polymer chain or less than 1 in 50 monomer units. Thisresult obviously confirmed that the CaH₂ mediated reaction sufficientlydepressed the side reactions.

[0159] 7. H₂O Effect.

[0160] H₂O is proved to cause side reactions such as hydrolysis of etherlinkage in this polymerization. This effect to the CaH₂ (or CaO)mediated reaction was verified by using CaO as mediator, so that waterwas allowed in the reaction. FIG. 9 shows the effect on the reactionkinetics of different CaO that contained different level of H₂O (w %,measured by TGA) as shown below Type of CaO Free H₂O H₂O as Ca(OH)₂ CO₂as CaCO₃ Flame dried 0.00% 0.00% 8.0% Vacuum dried 0.00%  2.0% 0.9%As-received 0.04%  3.7% 0.9%

[0161]FIG. 9 shows that the reaction speed increased with the increaseof the water content in the solution. Traces of water will efficientlypromote the reaction rate. However, with the water content level as highas 0.2% of the solution, a molecular weight reducing at the end ofpolymerization was found, indicating side reactions to cause chaincleavage. However, this side reaction seems depressed when the reactionwas conducted at lower temperature as shown in FIG. 9. In this case,high molecular weight polymers were obtained.

CHEMICAL EXAMPLES

[0162] 1. The Preparation of bis(tetrafluorostyrol)-hexafluorobisphenylDiether by Using CaH₂

[0163] Pentafluorostyrene (FSt, 1.941 g, 10.0 mmol) and4,4′-(hexafluoroisopropylidene) diphenol (6F-BPA, 1.345 g, 4.0 mmol)were dissolved in 12 mL DMAc in a 50 mL flask. The mixture was stirreduntil starting materials dissolved well. CsF (0.182 g, 1.20 mmol) andCaH₂ (0.42 g, 10.0 mmol) were added, the system was purged with Ar underfreeze, and then heated at 95° C. for 8 hr. The solution was cooled downto room temperature prior to the removal of salt by filtration, then thesolution was precipitated into acidic water, washed with water twice anddried under vacuum at room temperature for 24 hr to offer a white powderin a yield of 86%.

[0164] 2. The Preparation of bis(tetrafluorostyrol)-hexafluorobisphenylDiether by Using Molecular Sieves

[0165] FSt (24.3 g, 125.0 mmol) and 6F-BPA (16.8 g, 50 mmol) weredissolved in a solvent mixture of 80 mL DMAc and 85 mL benzene in a 550mL flask. A thimble filled with 20 mL 3 angstrom molecular sieves wasinserted between condenser and flask. The mixture was stirred untilstarting materials dissolved well. K₂CO₃ (13.8 g, 100 mmol) was added,the system was purged with Ar under freeze, and then heated and refluxed(101° C.) for 3 hr. The solution was cooled down to room temperatureprior to the removal of salt by filtration, then the solution was vacuumevaporated to remove benzene and was precipitated into acidic water,washed with water twice and dried under vacuum at room temperature for24 hr to offer white powder in a yield of 91%.

[0166] 3. The Preparation ofbis(tetrafluorostyrol)-2,2,3,3,4,4,5,5-octafluorohexane-1,6-diether byUsing NaH

[0167] NaH (95%, 2.22 g, 88.0 mmol) was dispersed in 50 mL dry THF in a250 mL flask, octafluorohexanediol (10.48 g, 40 mmol) in 20 mL THF wasdropped into the NaH mixture at room temperature. The reaction wasmaintained until no gas released. Then FSt 19.41 g, 100 mmol) in 40 mLTHF was added into the reaction mixture at one portion under vigorousstirring at 0° C., the solution was then warmed to room temperature andkept at RT for 30 min, followed by heating and refluxing for 2 hr. Thereaction mixture was filtered to remove solid and then precipitated intoacidic water, washed with water twice. A white powder with a yield of80.1% was obtained after being dried under vacuum overnight.

[0168] 4. The Preparation of Tetrafluorostyrol-1H, 1H-perfluoroheptaneEther by Using NaH

[0169] NaH (95%, 2.78 g, 110 mmol) was dispersed in 120 mL dry THF in a250 mL flask, 1H,1H-perfluoroheptanol (35.0 g, 100 mmol) in 40 mL THFwas dropped into the NaH mixture at room temperature. The reaction wasmaintained until no gas released. Then FSt 19.41 g, 100 mmol) in 40 mLTHF was added into the reaction mixture at one portion under vigorousstirring at −10° C., the solution was then warmed to room temperatureand kept at RT for 30 min, followed by heating and refluxing for 2 hr.The reaction mixture was filtered to remove solid and then was droppedinto acidic water. Yellow viscous oily liquid was precipitated onto thebottom, which was washed with water twice and then vacuum dried. Theproduct was purified by passing its solution in hexane through a shortsilica gel column, the then evaporating the solvent. This process offera colorless liquid in a yield of 80.7%.

[0170] 5. The Preparation of Fluorinated Poly(arylene Ether Ketone)(FPEK) by CaH) Method with CsF as Catalyst in DMAc.

[0171] Bis(pentafluorophenyl) ketone (DBP, 1.086 g, 3.00 mmol), 6F-BPA(0.992 g, 2.95 mmol) were dissolved in 16 mL DMAc in a 50 mL flask. Thereaction mixture was stirred until starting materials dissolved well.CsF (0.18 g, 1.2 mmol) and CaH₂ (0.25 g, 6.0 mmol) was added. Thesolution was protected with Ar, and stirred at 45° C. for 10 hr. Thesolution was filtered to remove salt, and then precipitated into acidicmethanol. The powder was washed with methanol twice and dried undervacuum for 24 hr to offer a white powder in a yield of 85%. The polymerwas characterized by GPC giving Mw=56,900 Da and PDI=3.0

[0172] 6. The Preparation of FPEK Mediated by CaH₂ and Catalyzed by KFin DMAc.

[0173] DBP (1.086 g, 3.00 mmol), 6F-BPA, (0.992 g, 2.95 mmol) weredissolved in 20 mL DMAc in a 50 mL flask The mixture was stirred untilstarting materials dissolved well. KF (0.07 g, 1.2 mmol) and CaH₂ (0.25g, 6.0 mmol) was added. The solution was protected with Ar, and stirredat 75° C. for 4 hr. The solution was filtered to remove salt, and thendropped into acidic methanol with agitation for precipitating polymer.The powder was washed with methanol twice and dried under vacuum for 24hr to offer a white powder in a yield of 87%. The polymer wascharacterized by GPC giving Mw=82,000 Da and PDI=3.5.

[0174] 7. The Preparation of FPEK Mediated by CaO and Catalyzed by KF inDMAc.

[0175] DBP (1.086 g, 3.00 mmol), 6F-BPA, (0.992 g, 2.95 mmol) weredissolved in 20 mL DMAc in a 50 mL flask. The mixture was stirred untilstarting materials dissolved well. KF (0.07 g, 1.2 mmol) and CaO (0.51g, 9.0 mmol) was added. The solution was protected with Ar, and stirredat 70° C. for 6 hr. The solution was filtered to remove salt, and thendropped into acidic methanol with agitation for precipitating polymer.The powder was washed with methanol twice and dried under vacuum for 24hr to offer a white powder in a yield of 88%. The polymer wascharacterized by GPC giving Mw=59.200 Da and PDI=3.1.

[0176] 8. The Preparation of FSt-FPEK with FSt as End-Cappers Mediatedby CaH₂ and Catalyzed by KF in DMAc.

[0177] FSt (1.281 g, 6.6 mmol), 6F-BPA, (10.087 g, 30.0 mmol) weredissolved in 80 mL DMAc in a 250 mL flask The mixture was stirred untilstarting materials dissolved well. CsF (0.21 g, 1.4 mmol) and CaH₂ (2.1g, 50 mmol) was added. The solution was purged with Ar under freeze andwas protected with Ar, and then stirred at 120° C. for 3 hr. Thesolution was cooled down to room temperature, followed by adding DBP(9.777 g, 27.0 mmol) in 30 mL DMAc. Then the solution was heated to 70°C. and stirred at this temperature for 4 hr. The solution was filteredto remove salt, and then dropped into acidic methanol with agitation forprecipitating polymer. The powder was washed with methanol twice anddried under vacuum for 24 hr to offer a white powder in a yield of88.8%. The polymer was characterized by GPC giving Mw=16,300 Da andPDI=1.8.

[0178] 9. The Preparation of FSt-FPEK with FSt as End-Cappers andPendant Groups by Molecular Sieve Method.

[0179] FSt (1.708 g, 8.8 mmol), 6F-BPA, (9.415 g, 28.0 mmol) weredissolved in DMAc/benzene (60/31, v/v) mixture in a 250 mL flask. Athimble filled with 20 mL 3 angstom molecular sieves was insertedbetween condenser and flask. The reaction mixture was stirred untilstarting materials dissolved well. K₂CO₃ (5.8 g, 42 mmol) was added, thesystem was purged with Ar under freeze, then protected with Ar, heatedand refluxed (117° C.) for 4 hr in dark (bath temp, 150-155° C.). Thesolution was cooled down to RT and was added with DBP (7.605 g, 21mmol), DMAc (30 mL) benzene (33 mL). The solution was purged with Aragain and then refluxed (108° C.) for 30 min (bath temp, 145° C.). Thereaction mixture was filtered to remove the salt, evaporated under highvacuum to remove benzene and then precipitated into acidic methanol,washed with methanol twice to offer white powder in a yield of 86%. Thepolymer was characterized by GPC giving Mw=26,500 Da and PDI=2.8.

[0180] 10. The Preparation of FSt-FPESO by Dehydrating CondensedRefluxing Solvents

[0181] Bis(pentafluorophenyl) sulfone (BPSO, 1.195 g, 3.00 mmol) 6F-BPA(0.975 g, 2.95 mmol) were dissolved in a solvent mixture of DMAc (12mL), benzene (9 mL) and THF (21 mL) in a 100 mL flask, A thimble filledwith 2.0 g CaH₂ was inserted between condenser and flask for trappingH₂O in condensed solvent. The reaction mixture was stirred untilstarting materials dissolved well. The solution was added with K₂CO₃followed by purging with Ar under freeze, and then heating and refluxing(80° C.) for 90 min. The solution was filtered to remove salt, and thenconcentrated (1/2) by vacuum evaporation and precipitated into acidicmethanol The white powder with a yield of 81% was obtained after thesample was washed with methanol and than dried under vacuum overnight.Mw=22,000, PDI=2.3.

[0182] 11. The Preparation of FPESO Mediated by CaH₂ and Catalyzed by KFin DMAc.

[0183] BPSO (1.195 g, 3.00 mmol) 6F-BPA (0.992 g, 2.95 mmol) weredissolved in 16 mL DMAc in a 50 mL flask. The mixture was stirred untilstarting materials dissolved well. KF (0.07 g, 1.2 mmol) and CaH₂ (0.25g, 6.0 mmol) was added. The solution was protected with Ar, and stirredat 60° C. for 7.5 hr. The solution was filtered to remove salt, and thendropped into acidic methanol with agitation for precipitating polymer.The powder was washed with methanol twice and dried under vacuum for 24hr to offer a white powder in a yield of 87%. The polymer wascharacterized by GPC giving Mw=70,000 Da and PDI=3.3.

[0184] 12. The Preparation of FPESO Mediated by CaH₂ and Catalyzed by KFin PC.

[0185] BPSO (1.195 g, 3.00 mmol) 6F-BPA (0.992 g, 2.95 mmol) weredissolved in 16 mL PC in a 50 mL flask. The mixture was stirred untilstarting materials dissolved well. KF (0.07 g, 1.2 mmol) and CaH₂ (0.25g, 6.0 mmol) was added. The solution was protected with Ar, and stirredat 60° C. for 12 hr. The solution was filtered to remove salt, and thendropped into acidic methanol with agitation for precipitating polymer.The powder was washed with methanol twice and dried under vacuum for 24hr to offer a white powder in a yield of 87%. The polymer wascharacterized by GPC giving Mw=70,300 Da and PDI=3.0.

[0186] 13. The Preparation of FPESO Mediated by CaH₂ and Catalyzed byCsF in PC.

[0187] BPSO (1.195 g, 3.00 mmol) 6F-BPA (0.992 g, 2.95 mmol) weredissolved in 16 mL PC in a 50 mL flask. The mixture was stirred untilstarting materials dissolved well. CSF (0.18 g, 1.2 mmol) and CaH₂ (0.25g, 6.0 mmol) was added. The solution was protected with Ar, and stirredat 50° C. for 3 hr. The solution was filtered to remove salt, and thendropped into acidic methanol with agitation for precipitating polymer.The powder was washed with methanol twice and dried under vacuum for 24hr to offer a white powder in a yield of 88%. The polymer wascharacterized by GPC giving Mw=89,200 Da and PDI=3.7.

[0188] 14. The Preparation of FSt-FPESO with FSt as End-Cappers andPendant Groups by Molecular Sieve Method.

[0189] FSt (1.708 g, 8.8 mmol), 6F-BPA, (9.415 g, 28.0 mmol) weredissolved in DMAc/benzene (40/24,v/v) mixture in a 250 mL flask. Athimble filled with 10 mL 3 angstrom molecular sieves was insertedbetween condenser and flask. The reaction mixture was stirred untilstarting materials dissolved well. K₂CO₃ (2.21 g, 16 mmol) was added,the system was purged with Ar under freeze, then protected with Ar,heated and refluxed (117° C.) for 4 hr in dark (bath temp, 150-155° C.).The solution was cooled down to RT, evaporated under vacuum to removebenzene and was added with BPSO (8.362 g, 21.0 mmol), CaH₂ (2.1 g, 50mmol) and PC (120 mL). The solution was purged with Ar again and thenheated at 60° C. for 90 min. The reaction mixture was filtered to removethe salt, and then precipitated into acidic methanol, washed withmethanol twice to offer white powder in a yield of 84%. The polymer wascharacterized by GPC giving Mw=38,800 Da and PDI=3.1.

1. A process for preparing a fluorinated poly(arylene ether) comprisingthe repeating unit:

wherein n provides a molecular weight up to 100,000, X represents one offollowing groups: none, ketone, sulfone, sulfide, ether,hexafluoroisopropylidene, αω-perfluoroalkylene, oxadiazole, and Y is4,4′-(hexafluoroisopropylidene)-diphenyl, 4,4′-isopropylidene diphenyl,3,3′-isopropylidene diphenyl, phenyl, or chlorinated phenol whichprocess comprises reacting a bis(pentafluorophenyl) compound and abisphenol or hydroquinone in the presence of a dehydrating agent and apolar aprotic solvent.
 2. The process of claim 1 wherein the dehydratingagent is selected from the group consisting of a molecular sieve, NaH,CaH₂, CaO, silica gel, activated Al₂O₃, CaSO₄, MgSO₄, and Na₂SO₄.
 3. Theprocess of claim 1 when carried out in the presence of areflux-temperature-reducing co-solvent.
 4. The process of claim 3wherein the co-solvent is selected from the group consisting of toluene,benzene and tetrahydrofuran.
 5. The process of claim 3 wherein thedehydrating agent is contained in a thimble located between a reactionflask and a condenser so that condensed solvent from refluxing passesthrough the dehydrating reagent.
 6. The process of claim 1 wherein saidpolar aprotic solvent is selected from the group consisting of dimethylacetamide, dimethyl sulfoxide, N-methyl-2-pyrrolidone (NMP), dimethylformamide and propylene carbonate.
 7. The process of claim 1 carried outin the presence of an alkali metal salt.
 8. The process of claim 7wherein the alkali metal salt is a carbonate.
 9. The process of claim 8wherein the wherein the alkali metal carbonate is selected from thegroup consisting of Na₂CO₃, K₂CO₃, Rb₂CO₃ and Cs₂CO₃.
 10. A process forpreparing a fluorinated poly(arylene ether) as described in claim 1mediated by CaH₂ or CaO and in the presence of catalytic amount of analkali metal salt in a polar aprotic solvent.
 11. The process of claim10 wherein the alkali metal salt is a fluoride.
 12. The process of claim11 wherein the alkali metal salt is selected from the group consistingof KF, RbF, and CsF.
 13. The process of claim 10 wherein the polaraprotic solvent is selected from the group consisting of dimethylacetamide, dimethyl sulfoxide, N-methyl-2-pyrrolidone (NMP), dimethylformamide and propylene carbonate.
 14. A process for preparing atetrafluorostyrene comprising a polymer or oligomer of the formula: a.Crosslinkable Polymers with FSt Groups End-Capped

b. Oligomers

in which n provides a molecular weight up to 30,000, X represents one offollowing groups: none, ketone, sulfone, sulfide, ether,hexafluoroisopropylidene, αω-perfluoroalkylene, oxadiazole, and Y is4,4′-(hexafluoroisopropylidene)-diphenyl, 4,4′-isopropylidene diphenyl,3,3′-isopropylidene diphenyl or —CH₂(CF₂)₂₋₁₂CH₂— which processcomprises reacting pentafluorostyrene with bisphenol and then with abis(pentafluorophenyl) compound in the presence of a dehydrating agentand a polar aprotic solvent.
 15. The process of claim 14 when carriedout as a one-pot reaction.
 16. A process for preparing a fluoropolymercomprising fluorostyrene residues as end-caps or as pendant groups ofthe formula:

wherein n, X and Y are as defined in claim 1 and m is from 1 to 20 whichprocess comprises polymerizing a compound of the formula 1 or 2

with a bis(pentafluorophenyl) compound as a one-pot reaction in thepresence of a dehydrating agent and a polar aprotic solvent.
 17. Theprocess of claim 16 wherein compounds 1 and 2 are present in apredefined ratio.
 18. A crosslinkable highly fluorinated oligomer, apoly(arylene ether) or a poly(alkylene arylene ether) with fluorostyreneresidues as end-cap groups or pendant groups in the oligomer or polymer,said oligomer or polymer having the formula: a. Oligomers

b. Crosslinkable Polymers with FSt Groups End-Capped

c. Crosslinkable Polymers with FSt End-Capped and Pendant Groups

wherein n and m are as defined in claim 16 and


19. A highly fluorinated poly(arylene ether oxidazole) comprisingrepeating units of the formula:

wherein n and Y are as defined in claim
 18. 20. A crosslinked polymerfilm with an adjustable refractive index comprising a mixture ofpolymers or oligomers as defined in claim 18.